This invention relates to medical catheters for target specific drug delivery.
Medical therapies may require the targeting of the therapy to a targeted patient site to maximize the therapeutic benefit and/or minimizing adverse effects to other organs or tissues outside the targeted patient site.
Huss and Reinhardt, U.S. Pat. No. 4,968,306 describes an elongated catheter assembly for intravascular delivery of intravenous therapeutic fluids. This assembly has a distal end having multiple pores which is sheathed by an outer proximal segment for variable exposure of delivery surface area by sliding the distal segment from the outer proximal sheath. A disadvantage of this assembly is that it results in a lack of homogeneity of pore placement and pore number for fluid discharge, which indicates a pore size of 2-20 microns.
Delgado, U.S. Pat. No. 3,640,269 describes a fluid delivery assembly having two flexible fluid-impermeable tubes open at one end and provided with an enlarged flexible permeable bag at the delivery segment. This bag is comprised of a membrane having uniform porosity less than 0.5 microns and having a water permeability of at least 60 mL/minute/cm as a description of fluid permeability. While this design is capable of uniform fluid delivery to tissues adjacent to the permeable bag, a disadvantage of this assembly is its inability to be specifically targeted to a patient site due to the flexible distal bag.
Thus, there is a need for a device that provides uniform distribution of therapeutic agents to a targeted patient site or multiple targets sites. There is also a need for a device that provides this uniform distribution, yet has sufficient rigidity for accurate placement of the device so that it can deliver therapeutic agents to the targeted patient site or multiple sites.
A new medical catheter has now been discovered that provides uniform distribution of therapeutic agents to a targeted patient site. Moreover, the medical catheter of the present invention has a unique structure that permits it to be accurately placed so that it can uniformly distribute therapeutic agents to the targeted patient site.
In a one embodiment of the present invention, the catheter has at least two distal ends, and a proximal end joined to the two distal ends via a connector, such as a xe2x80x9cYxe2x80x9d connector having three legs. Thus, the two distal ends and the proximal end are each located at a separate ends of the legs of the connector. Preferably, restrictors are placed in each leg of the connector. A restrictor is a structure that provides a significant pressure drop when fluid flows through that structure. The restrictors of the present invention provide structure to balance the flow for a multiple catheter system. The restrictors can be made of any suitable material, e.g. a powder material such as sintered metal powder. In this embodiment, diffusers are placed at the distal ends. A diffuser is a structure that diffuses and delivers a therapeutic agent over a large surface area as opposed to a single point source. In this embodiment, the diffusers and restrictors, which are in each leg having a distal end, are separated from each other. Preferably, the diffuser is at the tip of each distal end, and the each restrictor is upstream of the distal end. This construction is particularly useful for delivery of drugs via multiple catheter ends. For example, drug delivery to the two different hemispheres of the brain may be achieved, and the present invention can deliver drugs to each hemisphere substantially equally because of the restrictor(s) upstream of the distal ends, rather than at the distal ends as are the diffusers. In this embodiment of the present invention the following benefits are obtained by separating the diffuser and the restrictor: (1) increase in design options for the catheter tip; (2) improved reliability of catheter tip that is implanted in the brain tissue; and (3) reduced need to test the restrictor structure for biostability.
In another embodiment of the present invention, a restrictor is placed upstream of the Y connector as well, so that there is a restrictor in all three legs of the catheter joined by the Y connector. This construction provides additional benefits. For example, having the restrictor upstream of the Y connector acts as a pre-filter, and thus removes any particulates prior to the Y connector. This pre-filter function reduces particulates to the restrictors downstream of the Y connector, thus reducing the potential for different pressure drops and flow rates through the restrictors downstream of the Y connector, and ultimately the flow rate of the delivered drug through the diffusers at the distal ends. In addition, this embodiment eliminates the possibility for insertion of a catheter where only one restrictor is downstream of the Y connector, and one restrictor is upstream of the Y connector.
In another embodiment, the catheter of the present invention comprises a rigid assembly having a rigid tube for positioning the distal end of the catheter near a targeted patient site or sites. the distal end of the catheter has a rigid porous delivery segment having a porosity less than 0.50 microns for achieving homogenous delivery to the targeted patient site. More specifically, in this embodiment, the catheter of the present invention has a rigid assembly having an open tube having a distal end, the distal end having sintered metal powder, for example, metal microspheres to provide uniform porosity of the delivery segment. In this embodiment, the distal end comprises at least one uniform surface made of sintered metal powder. Preferably, the sintered metal powder can be made of any light-weight, high tensile strength material, e.g., tungsten, titanium or tantalum. In this embodiment, the rigid assembly functions as both a diffuser and a restrictor. The sintered metal rigid assembly of this embodiment can be fabricated using a single cavity carbon mold, and a mold insert. Alternatively, the sintered metal rigid assembly can be fabricated using powdered metal and pyrogenic sintering, such as high pressure plus pyrogenic sintering. Sintered metal rigid assemblies can be positioned at the distal ends of separate legs of a catheter for placement at multiple patient targets. The distal ends can each join to a connector (e.g., a xe2x80x9cYxe2x80x9d connector) for connection to a single therapy source. The sintered metal rigid assembly of this embodiment unctions as both a fluid restrictor and a fluid diffuser. Thus, the diffuser and restrictor functions can be combined, as in a membrane tip, or separated, with the restrictor being upstream of the diffuser in each leg of the catheter.
When it is desired for the sintered metal powder to be radiopaque, a radiopaque material can be used, such as tungsten, titanium or tantalum. These metals are non-magnetic, and therefore are safe within a magnetic imaging environment.
An objective of the present invention is to provide for multiple catheter ends for drug delivery arising from a single pump source. The present invention provides a catheter construction that provides desired distribution in a targeted area of the patient, such as giving medications intraparenchymally into tissue. Drug delivery by the present invention can be to an organ, and uniform distribution to that organ may be desired. It is a further objective of the present invention to provide for multiple catheter ends, at least two, into the brain of patient, and more specifically, into the two different hemispheres of the brain, with each catheter end supplied with therapeutic drugs by the same pump, and with the fluid flow of the therapeutic agent being substantially equal between the two catheter ends. It is usually desirable to have equal amounts of drug delivered to both brain hemispheres.
Another objective of the present invention is to provide a catheter to diffuse a therapeutic agent over a larger surface area than from a single point source. This structure results in a decrease in fluid flux and reduces potential for damaging tissue near the infusion site. In order for equal or near equal bilateral drug delivery to occur, two distal ends are required since fluid delivered from one distal end to a target site at one hemisphere will not deliver fluid to the other hemisphere.
The present invention can be used for many drug delivery applications, including but not limited, to intraparenchymal or tissue infusion (such as brain tissue infusion), intrathecal drug delivery and intracerebral ventricular (ICV) drug delivery, or any drug infusion into a fluid filled space or to a tumor.